Question

1)A car of mass 1330 kg is traveling at 28.0 m/s. The driver applies the brakes to bring the car to rest over a distance of 79.0 m. Calculate the retarding force acting on the car.

I don't get it. What is retarding force? gravity has to factor in somewhere due to acceleration

(79.0/28.0)*1330
3752.5

2)What should be the angle between two vectors of magnitudes 3.20 and 5.70 units, so that their resultant has a magnitude of 6.10 units?

6.1 = sqrt(5.7 + 3.2cos(t)² + (3.2sin(t)²
37.21 = 35.69 + 36.48cos(t) + 7.04cos²(t)
7.04cos²(t) + 36.48cos(t) -1.52 = 0

98.2 im really confused

Answer 1

I don't know anything about physics -- but a retarding force must be the brakes that are applied because they retard the motion of the car.

You could have checked a dictionary for the definition of retarding.

Answer 2

When stopping, retarding force is friction. Brakes make the wheels slow, and the rubber acts on the road to slow vehicles. Gravity only assists friction.

2. Use the law of cosines. You have three sides, solve for the angle